由时间服务器产生的一个误会(by quqi99)

作者：张华 发表于：2026-07-23
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自从我换老板之后，我感觉我每次都是准时参会的，但我老板总喜欢ping我，原来全是时间服务器惹得祸。我发现mattermost和我的手机上的时间都比我本地电脑的时间快一分钟，而我是看着本地电脑的时间准时参会的，所以我每次会比别人晚一分钟，所以误会就产生了。

1, The automatic time synchronization has been turned on, but the time synchronization was not successful (System clock synchronized: no)

hua@y9000p:~$ timedatectl status Local time: 四 2026-07-23 10:15:40 CST Universal time: 四 2026-07-23 02:15:40 UTC RTC time: 四 2026-07-23 02:15:14 Time zone: Asia/Shanghai (CST, +0800) System clock synchronized: no NTP service: active RTC in local TZ: no

2, My machine does not have an IPv6 address, but ntp.ubuntu.com is using an IPv6 address (2620:2d:4000:1::3f)

hua@y9000p:~$ timedatectl timesync-status Server: 2620:2d:4000:1::3f (ntp.ubuntu.com) Poll interval: 34min 8s (min: 32s; max 34min 8s) Packet count: 0 hua@y9000p:~$ ip -6 route get 2620:2d:4000:1::3f RTNETLINK answers: Network is unreachable hua@y9000p:~$ ip addr show wlp130s0f0 3: wlp130s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 98:fe:3e:20:6a:d4 brd ff:ff:ff:ff:ff:ff inet 192.168.3.130/24 brd 192.168.3.255 scope global dynamic noprefixroute wlp130s0f0 valid_lft 552060sec preferred_lft 552060sec inet6 fe80::300:c64:a190:e6ee/64 scope link noprefixroute valid_lft forever preferred_lft forever

3, It should be because ntp.ubuntu.com timed out when using an IPv4 address, so it switched to using an IPv6 address.

hua@y9000p:~$ journalctl -u systemd-timesyncd -b --no-pager |grep -i 'timed out' |wc -l 2584 hua@y9000p:~$ journalctl -u systemd-timesyncd -b --no-pager |grep -i 'timed out' |tail -n1 7月 23 09:58:32 y9000p systemd-timesyncd[1792]: Timed out waiting for reply from 185.125.190.58:123 (ntp.ubuntu.com). hua@y9000p:~$ resolvectl query ntp.ubuntu.com ntp.ubuntu.com: 2620:2d:4000:1::41 -- link: wlp130s0f0 2620:2d:4000:1::40 -- link: wlp130s0f0 2620:2d:4000:1::3f -- link: wlp130s0f0 91.189.91.157 -- link: wlp130s0f0 185.125.190.58 -- link: wlp130s0f0 185.125.190.57 -- link: wlp130s0f0 185.125.190.56 -- link: wlp130s0f0

4, But this command (nc -vzu ntp.ubuntu.com 123) is successful now.

hua@y9000p:~$ nc -vzu ntp.ubuntu.com 123 Connection to ntp.ubuntu.com (185.125.190.58) 123 port [udp/ntp] succeeded!

5, After adding the domain ntp.ubuntu.com into whitelist in my router

hua@y9000p:~$ journalctl -u systemd-timesyncd -b --no-pager -f ... 7月 23 09:58:32 y9000p systemd-timesyncd[1792]: Timed out waiting for reply from 185.125.190.58:123 (ntp.ubuntu.com). 7月 23 10:34:01 y9000p systemd-timesyncd[1792]: Contacted time server 185.125.190.58:123 (ntp.ubuntu.com). 7月 23 10:34:01 y9000p systemd-timesyncd[1792]: Initial clock synchronization to Thu 2026-07-23 10:34:01.939524 CST.

6, Maybe I can also use the following configuration instead.

sudo timedatectl set-timezone Asia/Shanghai sudo sed -i 's/#RootDistanceMaxSec=5/RootDistanceMaxSec=999999999/' /etc/systemd/timesyncd.conf sudo sed -i 's/#NTP=/NTP=ntp.aliyun.com/' /etc/systemd/timesyncd.conf systemctl restart systemd-timesyncd